The present invention relates to a address decoding system for a micro-controller system and, more particularly, to an address decoding system particularly suited for postage metering applications.
In postage metering machine applications, and like machine applications, a micro-controller system is employed to control both machine control function and system functions. System functions, for example, in the postage metering area, refer to functions as funds accounting, external device interface and user interface function. Machine control functions, for example, refers to such functions as motor control, print control and sensor control.
In electronic postage metering machine, and like devices, it is customary to develop a specific micro-controller system for each model postage meter model to accommodate the unique control requirements of each meter model. Conventionally, a micro-controller system, of the type customarily used in postage metering applications, is comprised of a programmable microprocessor in bus communication with a read-only memory (ROM) or program memory, random access memory (RAM), non-volatile memories (NVMs) and an application specific integrated circuit (ASIC). The ASIC chip provides a unique or custom set of system capabilities particular to the employing postage meter model in response to directives from the microprocessor. The ASIC chip also controls the addressing of data to the memory units. One of the factors which have predicated customizing of the ASIC is the size of the memory units. The process of memory mapping is a conventional practice of assigning fixed memory space to an addressable range based on the size of memory devices intended to be used in the particular control system of the specific electronic postage meter model. Because of this address range tailoring, it has been considered not possible to interchange the control system of one electronic postage meter model for that of another electronic postage meter model where the control requirements between the two electronic postage meters is substantially different necessitating increased memory space.